[GHC] #8441: Allow family instances in an hs-boot file

[GHC]

#8441: Allow family instances in an hs-boot file
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        Reporter:  goldfire          |                Owner:  ezyang
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.7
      Resolution:                    |             Keywords:  backpack,
                                     |  TypeFamilies, hs-boot
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by ezyang):

 So, this is actually not so trivial even for Backpack. The problem is that
 data families turn into a rather delicate constellation of interface
 declarations, and the way signature merging is written, I have to teach it
 how to hoover these all up BACK into (deduplciated) FamInsts, so that when
 I write it out to an interface for the final time, everything is kosher.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8441#comment:11>
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